1. Field of the Invention
This invention generally relates to a liquid crystal display device, and more particularly to a liquid crystal display device having a pixel repairing structure.
2. Description of the Related Art
A liquid crystal display device typically includes a liquid crystal panel, which is formed by a pair of substrates, and a plurality of liquid crystal cells formed on the liquid crystal panel. The substrates are maintained apart from and parallel to each other, and a liquid crystal material is sandwiched between the substrates. The liquid crystal material changes its optical characteristics in response to applied voltage signals.
Millions of pixel electrodes are formed on one of the substrates and arranged in a matrix type for applying voltage signals to the liquid crystal cells, and a common electrode is formed on the other one. Each of the pixel electrodes is connected to a thin film transistor (TFT), and applies a voltage signal to the liquid crystal cell according to a data signal received by the connected thin film transistor. However, when one of the pixel electrodes or the transistors connected to the pixel electrodes has a defect, a defective pixel may occur and thus cause a bright dot or dark dot on the liquid crystal display device. Therefore, a repair for defective pixel is necessary so that the observer will not perceive the defective pixel.
U.S. Pat. No. 6,833,882 B2 issued to Lee on Dec. 21, 2004 (hereinafter, Lee), which is incorporated herein by reference, has discussed some conventional methods illustrated in its FIGS. 1 and 2 for repairing the defective pixel and the drawbacks of those conventional methods. In order to overcome the drawbacks of those conventional methods, Lee has disclosed a liquid crystal display device and a pixel repairing method for increasing aperture ratio and repair efficiency. In Lee's method, when a defective pixel occurs, a data signal from a data line to an associated TFT will be cut by using a laser; thereafter, the defective pixel is connected with a repair drain electrode of a previous TFT so that the defective pixel is repaired. However, the repaired defective pixel of Lee can not realize a normal color as a normal pixel used to do, but only can realize the same color as a previous pixel. Thus, if a liquid crystal panel is larger than 17 inches, the repaired defective pixel may be easily perceivable by inputting the data of the previous pixel.